New EEVblog BM786 Multimeter

[rsjsouza]

Quite interesting indeed. A BM789 with dual displays...

[Antrus]

And PC connection. But the display is most likely 10,000 counts on photo.

[AVGresponding]

I'm guessing 6000 counts, and it's just a misprint? Though it is stated twice in the spiel...

The MD 9060 seems to be a rebadged BM869S

[EEVblog]

Hi all. I found a strange hybrid from a Brymen - Metrel MD 9055, Two displays. 60,000 counts are declared.

That is oddball, but it's certainly not 60,000 count.

[Brumby]

The main display is clearly capable of only 4 digits, but the secondary display looks like it has space to do 6.

From the spec sheet:

[Antrus]

Dual display is fake. According to the instructions, a complete analogue of 789. The sensation did not work out.

[starfry]

Hello, I would like to get a BM786 in the UK.

Simons Electronics has some but he charges £10 for UK shipping whereas I have prime so free shipping from Amazon. Plus it's also easier for returns should the unlikely need arise.
Will amazon.co.uk have any stock soon?

https://www.amazon.co.uk/EEVBlog-exclusive-Brymen-BM786-multimeter/dp/B08N61LF4Z
https://simonselectronics.co.uk/product/bm786-eevblog/

[EEVblog]

Hello, I would like to get a BM786 in the UK.

Simons Electronics has some but he charges £10 for UK shipping whereas I have prime so free shipping from Amazon. Plus it's also easier for returns should the unlikely need arise.
Will amazon.co.uk have any stock soon?

Sorry no plans to restock amazon UK, I got dicked around way too much by Amazon UK

[mwb1100]

welectron.com sells the BM786 with 10 Euro worldwide shipping.  I don't know how the exchange from Euro to GBP would work out or if they'd have to charge the VAT (they don't when shipping to the US).  You can email them for an eevblog discount code which might tip the scales for you.

[starfry]

Thanks, I've emailed welectron as suggested but haven't had a reply yet. However I feel that shipping from EU into UK is now more hassle than it's worth.

I've spent far too long looking in to this but the conclusion I've reached is that the BM257s is the best bang-for-buck for me. This is available from Telonic for £99.34 (plus another £20.49) for the optional USB interface (so £119.83) and they do free shipping. The BM235 is £85.14 and the BM869s is £205.12 + £39.40 for the USB interface (so £244.52). I presume Telonic is an ok place to buy from ?

My needs are mostly around hobby microcontroller projects (arduino, ESP8266, RaspberryPi, etc) with the occasional need to check presence of a UK 220-240 voltage in relation to such projects. I'll never come into contact with anything beyond domestic supply. I started out looking at Anengs and Uni-T but decided, after reading on this forum, to pay a little more and get something better. I wanted an EEVBlog one but the lack of supply in the UK led me to discover Telonic (by web search) and the choices available there (I was looking for the BM829s but they don't appear to carry it). Being pragmatic about my use-case, features and cost I think the BM257s hits the spot. I found , although old, quite informative.

[mwb1100]

However I feel that shipping from EU into UK is now more hassle than it's worth.

When I bought from them, shipping to the US wasn't a problem in the slightest - just had to pay the 10 Euro worldwide shipping charge.  Of course, it's possible that different countries might cause different outcomes.

I've spent far too long looking in to this but the conclusion I've reached is that the BM257s is the best bang-for-buck for me.

I bought a BM257s (from TME I think), and it's definitely nice.  Very compact, but with a nice sized display.  The only drawback for me is that the backlight only stays on for around 30 seconds, which I find very annoying.  Backlights should stay on for at least 5 minutes in my opinion. Let me worry about the batteries!

I have also read complaints that the diode test apparently doesn't have the oomph to light up some LEDs.  This isn't a problem for me since I haven't had that need.
  -

[starfry]

I also read about the 257s diode test but I think I can live with that, and the short backlight.

So the difference between Welectron and Telonic boils down to the following

* brymen-bmp-25x-soft-carry-pouch
* brymen-bl21s2-t4sc-cat-iv-1000v-test-leads

Since this is going to live on my bench I don't think I'll miss the pouch but what about the test leads - what's the real difference there between the "standard" ones - does this really matter for someone at my microcontroller hobbyist level ?

[mwb1100]

welectron sells the BM257s in two "editions":

  - standard which comes with PVC leads and no carry case
  - "Edition+" which come with the BL21S2-T4SC Silicone leads and the carry case.

The Edition+ is about 10 Euro more than the standard configuration (excluding VAT: 110 euro vs 92 euro)

Looks like the Telonic deal is equivalent to welectron's "Edition+".

The silicone leads are much nicer than the standard PVC leads.  They also have screw on banana adapter bits that can come in handy at times - if you can manage to keep track of them.

welectron sells the silicone leads on thier own for about 10 Euro. So you you have no need for the carry case you might want to consider getting the standard configuration and add the silicone leads to the cart so that instead of the carry case you get a spare set of leads.

Of course, if Telonic is selling the "Edition+" kit for the same as welectron sells the standard kit, go with Telonic.

[starfry]

Looks like the Telonic deal is equivalent to welectron's "Edition+".

I don't think Telonic's is like the edition+ is it? Unless I missed something on their page?

I'm most likely to order from Telonic regardless as I can't be bothered with all the import hassle and not knowing what I'll be charged. Bloody brexit!

[SebastianH]

Maybe I'm missing something, then I have to apologize... Is there any official (or inofficial) calibration & adjustment procedure available to regular customers? From my quick experiments it seems like you enter the cal mode by switching the BM78x off, pressing and holding REC and then selecting Resistance (within 1 sec or so; CALi is displayed). But it would be very helpful to know when the meter saves the constants (Press SELECT?) and also whether it's possible to only calibrate certain ranges (don't really care about 300V and 1000V and don't have the equipment to do that properly anyway). Switching it off after the -30.000V point seems to either disregard any other setting or I did something else incorrectly.

Thanks in advance

[EEVblog]

Maybe I'm missing something, then I have to apologize... Is there any official (or inofficial) calibration & adjustment procedure available to regular customers? From my quick experiments it seems like you enter the cal mode by switching the BM78x off, pressing and holding REC and then selecting Resistance (within 1 sec or so; CALi is displayed). But it would be very helpful to know when the meter saves the constants (Press SELECT?) and also whether it's possible to only calibrate certain ranges (don't really care about 300V and 1000V and don't have the equipment to do that properly anyway). Switching it off after the -30.000V point seems to either disregard any other setting or I did something else incorrectly.

Brymen do not release their calibration procedure publicly.

[SebastianH]

Ok, good to know. Thanks anyway!

[JDW]

What is the expected BATTERY LIFE for the BM786 with fresh Alkaline batteries, backlight off? 

We know the 121GW is 500 hours with BT and the backlight off, so I'm curious about the BM786.

[J-R]

This greatly depends on the mAh capacity of the batteries.  The power consumption for various modes is listed on page 22 of the manual.  You can run the calculations and get a number based on ideal conditions.

[JDW]

This greatly depends on the mAh capacity of the batteries.  The power consumption for various modes is listed on page 22 of the manual.  You can run the calculations and get a number based on ideal conditions.

One could argue the same about the 121GW, yet it's manual says >500 hours, which is a nice guide to have.  Not too precise maybe, but still a nice rough estimate, which is really all I am seeking.

I don't know the best way to calculate battery life for the BM786.  If all the batteries are in series, then we would take the mAh rating of one, and I assume that to be about 850mAh for a single Alkaline AAA, which at an 8mA meter draw (I do DC work, not AC) would mean just over 100 hours:

https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-battery-life

[Fungus]

I don't know the best way to calculate battery life for the BM786.  If all the batteries are in series, then we would take the mAh rating of one, and I assume that to be about 850mAh for a single Alkaline AAA, which at an 8mA meter draw (I do DC work, not AC) would mean just over 100 hours:

Yep, that's how to calculate it....

One could argue the same about the 121GW, yet it's manual says >500 hours, which is a nice guide to have.

The 121GW uses AA batteries with about 4x the capacity. From that we can conclude that the power consumption must be similar. 

[J-R]

I think it's best to start by pulling up the datasheet of the batteries you are using.  For example, here are some Energizer AA and AAA alkaline datasheets:
https://data.energizer.com/pdfs/e91.pdf
https://data.energizer.com/pdfs/e92.pdf

The lowest published capacity and current draw data point for both is 25mA, so ~3,000mAh for AA and ~1,150mAh for AAA.  Even though both DMMs draw less than half that current, given the low-voltage cutoffs of the DMMs I think the numbers are probably reasonable as-is for this theoretical exercise.  Some of the batteries' capacity will be unusable.

The BM78x has 3xAAA batteries, and the 121GW has 4xAA.  The mA draw for each that is published is based on the operating voltage of the DMMs, and we know both are wired to run the batteries in series, so for runtime calculations you would simply use the mAh capacity of one battery.

One variable is that devices typically require a specific amount of power (V*A) to run, so as the voltage drops, the current will increase to compensate, and vice-versa.  For the 121GW it might be 30mW (4*1.5V*5mA) and for the BM78x it might be 36mW (3*1.5V*8mA).  We have to make some assumptions.

So for a true number, you would have to characterize the DMM with a power supply or do real-world tests with actual batteries.  Another variable is the point at which each DMM begins to become inaccurate, even though it is still "operating". 

However, for back of the envelope calculations, I think we can start with:
121GW - 3,000mAh/5mA=600 hours maximum
BM78x - 1,150mAh/8mA=143.75 hours maximum

The BM78x manual states the low battery indicator kicks in at 3.7V, which is 1.23V per cell.  That is leaving a lot on the table.  So I would lean towards ~100 hours as being more realistic.

The 121GW has a published life of 500 hours typical, and that seems like a reasonable number at face value.

[Fungus]

The BM78x manual states the low battery indicator kicks in at 3.7V, which is 1.23V per cell.  That is leaving a lot on the table.

Yep, but I hope nobody is thinking of using ordinary Alkalines in one of these.

Get some Eneloop AAAs. Discharge curve here.

Image courtesy of forum member HKJ: https://lygte-info.dk/

[J-R]

What, 99% of handheld DMMs ship with alkaline cells, then probably 99% of the time those are replaced with alkaline cells...  Leaks are rare, all things considered.

[EEVblog]